Electron discharge device



1955 J. ROTHSTEIN ELECTRON DISCHARGE DEVICE Filed Oct. 2, 1950 INVENTOR.

JEROME ROTHSTEIN QOCIDQOE Om BY W 22 d #7 far/1e United States Patent ELECTRON DISCHARGE DEVICE Jerome Rothstein, Belmar, N. J.

Application October 2, 1950, Serial No. 188,041

6 Claims. (Cl. 315-3.5)

(Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to electron discharge devices, particularly to traveling wave tube amplifiers in which a gaseous discharge device is employed as the signal propagating circuit.

In the conventional traveling wave tube employing a metallic helix as the radio frequency signal propagating circuit, an electron beam is shot through the axis of the helix or along the outer surfaces thereof in a direction parallel to its axis. As an externally applied signal, or traveling wave, is propagated along the helix, the established electromagnetic field is in coupling relationship to the electron beam. Thus, when the velocity of the electron beam is made substantially equal to the axial phase velocity of the propagated signal, amplification is achieved by the interaction between said beam and the electric component of said field. Since the operation of the tube depends on the fact that the wave and electrons travel with about the same velocity, it can readily be seen that the gain of the tube is limited by the narrow limits within which the beam voltage has to be controlled.

It is therefore an object of my invention to provide an improved traveling wave tube amplifier which avoids the above-mentioned limitation.

It is another object of my invention to provide an improved traveling wave tube amplifier wherein the resistivity of the signal propagating circuit may be controlled.

It is another object of my invention to provide a traveling wave tube amplifier employing a gaseous discharge device as the signal propagating circuit.

In accordance with my invention there is provided a vacuum tube having means for producing a narrow or constricted beam of electrons, and an energy absorbing circuit in the form of gaseous discharge device placed adjacent to the stream of electrons and coaxially arranged relative to the axis of the tube. The gas is contained in a tubular helical structure which is in coupling relationship to the electron beam, and means are provided to vary the resistivity of the gas filled helix by controlling the intensity of gas discharge.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing.

In the single figure of the drawing there is shown, an elevation, in part section, of a traveling wave tube embodying my invention.

Referring now to the drawing there is shown a traveling wave tube designated generally at 2 comprising an electron gun section 4 which includes cathode 6 and beam forming anode 8, a collector plate 10, and a tubular gas-filled helical conductor 12 intermediate said gun section and said collector plate. Tubular helix 12 is hermetically sealed at both ends as shown at 14 and 16,

Patented Oct. 25, 1955 and is filled with a suitable discharge gas 17 such as helium, argon, mercury, or any other suitable inert gas. Said helix may be made of glass, quartz, or any suitable glassy or ceramic material impervious to the gas contained therein.

Gasfilled helix 12 is axially aligned with electron beam 18 which is projected from electron gun 4. It is to be understood that cathodes in combination with a beam forming anode for producing and directing a beam of electrons are old and that any electron gun structure which will produce an electron beam of the desired current strength and velocity may be employed. The supporting means of helix 12 inside the tube have been omitted from the drawing for the sake of simplicity but it will be understood that they may be of any convenient and suitable type such as precision drawn low-loss glass tubing.

As illustrated, coupling collar 20 is positioned at one end of helix 12 and coupling collar 22 is positioned at the other end thereof, the ends of the helix passing therethrough. Portions of waveguide or coaxial cable, not shown, may be coupled to said collars in the usual manner to serve as radio frequency signal input and output circuits. Projecting into the ends of helix 12 through lead-in seals 14 and 16 are metallic electrodes 24 and 26 respectively. Gas discharge control circuit 28 is connected across'said electrodes to control the intensity of the gaseous discharge within the tubular helix and thereby control the resistivity of the gas. Since this type of control circuit is generally well known, complete details of this circuit are not shown in order to avoid unnecessary complications. For example, gas-discharge control circuit 28 may comprise a suitable ballast resistance or impedance greater in magnitude than any negative resistance which may be exhibited by gas-filled helix 12 when the gas is made conducting. Thus, the series circuit comprising plasma 17, electrode 24, gas-discharge control circuit 28, and electrode 26 permits effective con trol of the intensity of the gaseous discharge at all times. By this arrangement, a positive resistance, larger in magnitude than the negative resistance to be controlled, is connected in series with said negative resistance to effectively control the resistivity of gas-filled helix 12. The intensity of the discharge may be varied by modulator source 30, the output of which is connected to discharge control circuit 28. A D. C. potential may be applied between electrode 24 and cathode 6 by battery 32 or any other suitable source to maintain gas-filled helix 12 at a desired potential with respect to electron gun 4. This potential is of such magnitude that the velocity of the electron beam is made substantially equal to the axial phase velocity of the input signal as it is propagated along the helix. As shown, a suitable positive potential may be applied to collector anode 10 in the usual manner.

To prevent accumulation of charge and consequent interference with the electron beam, the outer surface of tubular helix 12 may be thinly coated as at 34 with carbon, platinum or any other material to form a high resistivity coating. This semi-conductive, or high resistance, metallic sheath permits leakage of electrons which may accumulate along the outer surface of helix 12, without appreciably affecting the leakage of electromagnetic flux. For completing the electron leakage path, collars 20 and 22 are provided with spring-like metallic stubs 36 and 38 which are in contact with high resistive coating 34 at the input and output ends of helix 12.

In operation, the electron beam interacts with the electric component of the electromagnetic field established by the input radio frequency signal to achieve amplification of said signal as it is propagated along gas-filled tubular helix 12. Said electric component is assumed to be parallel to the axis of the helix and in coupling relationship to said electron beam. As indicated above,

the gaseous discharge within the tubular helix is controlled by discharge control circuit 28, which in turn, may be controlled by the output of modulator source 34. By controlling the amount of discharge excitation, the resistivity of gas-filled tubular helix 12 may be varied. Thus, with no discharge, tubular helix 12 may be considered as a dielectric helix with a semi-conducting sheath, While for full discharge, helix 12 may be considered as a metallic helix. For a metallic helix, the radio frequency energy may be considered as traveling essentially in the space between the turns of the helix. For a dielectric helix, the radio frequency energy may be considered as essentially in the dielectric material, but with a different amount of coupling to the electron beam than in the case of the metal helix. It can readily be seen that by varying the discharge current the coupling between the radio frequency energy and the electron beam may be varied, thus controlling the gain of the tube.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is therefore aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In an electron discharge device having at one end thereof means for projecting a beam of electrons over a predetermined path with a predetermined velocity and electron collector means at the other end thereof, a gasfilled tubular conductive helix intermediate said projecting means and said collector anode, said helix being adjacent the path of said beam and in coupling relation thereto, a pair of spaced electrodes within said gas-filled helix for establishing an electric discharge in said gas filling to control the resistivity thereof, means for propagating an electromagnetic wave at approximately said predetermined velocity along said gas-filled helix whereby the electrons are exposed to interaction with the electric field associated with the propagated wave, and means enveloping the outer surface of said helix for preventing the accumulation of electrons on the outer surface of said gas-filled helix.

2. In an electron discharge device having at one end thereof means for projecting a beam of electrons over a predetermined path with a predetermined velocity and electron collector means at the other end thereof, a gasfilled tubular conductive helix intermediate said projecting means and said collector anode, said helix being adjacent to the path of said beam and in coupling relation thereto, electrode means in the ends of said helix for establishing an electric discharge in said gas filling to control the resistivity thereof, means for propagating an electromagnetic wave at approximately said predetermined velocity along said gas filled helix whereby the electrons are exposed to interaction with the electric field associated with the propagated wave, and means enveloping the outer surface of said helix for preventing the accumulation of electrons on the outer surface of said gas-filled helix.

3. A high-frequency electronic device comprising a gas-filled tubular conductive helix, means for propagating an electromagnetic wave along said helix at a predetermined velocity, an electron source adjacent one end of said helix, an electron collector adjacent the other end of said helix, means connected to said electron source for projecting an electron beam through the center of said helix at approximately said predetermined velocity whereby the electrons are exposed to interaction with the electric field associated with the propagated wave, the outer surface of said helix being coated for the entire length thereof with a metallic sheath of high resistivity to prevent electrons from accumulating on said outer surface, and electrode means in the ends of said helix for establishing an electric discharge in said gas filling to control the resistivity thereof.

4. In an electron discharge device comprising a vacuum tube having an electron source at one end thereof and a collector anode at the opposite end thereof, means connected to said electron source for projecting a beam of electrons in a predetermined path with a predetermined velocity, a gas-filled tubular conductive helix intermediate said electron source and said anode, said helix being coaxial with the path of said beam and in coupling relation thereto, means enveloping said helix for preventing the accumulation of electrons on the outer surface of said gas-filled helix, means for propagating an electromagnetic wave along said gas-filled helix to produce thereon a component electric field of said wave parallel to the direction of motion of said electron beam, and electrode means in the ends of said helix for establishing an electric discharge in said gas filling to control the resistivity thereof.

5. In an electron discharge device comprising a vacuum tube having an electron source of one end thereof and a collector anode at the opposite end thereof, means connected to said electron source for projecting a beam of electrons in a predetermined path with a predetermined velocity, a gas-filled tubular conductive helix intermediate said electron source and said anode and in coupling relation to the path of said beam, the outer surface of said helix being coated for the entire length thereof with a metallic sheath of high resistivity to prevent electrons from accumulating on said outer surface, means for propagating an electromagnetic wave along said gas-filled helix to produce thereon a component electric field of said wave parallel to the direction of motion of said beam, and electrode means in the ends of said helix for establishing an electric discharge in said gas filling to control the resistivity thereof.

6. A high-frequency electronic device comprising a gas-filled tubular conductive helix, means for projecting an electromagnetic wave along said tubular helix, an electron source adjacent one end of said helix, an electron collector adjacent the other end of said helix, means connected to said electron source for projecting an electron beam axially through said tubular helix whereby the electrons are exposed to interaction with the electric field associated with the propagated wave, electrode means connected between the ends of said helix for establishing an electric discharge in said gas filling to control the resistivity thereof, and a metallic sheath of high resistivity enveloping the outer surface of said helix to prevent electrons from accumulating thereon.

References Cited in the file of this patent UNITED STATES PATENTS 2,064,469 Haetf Dec. 15, 1936 2,228,327 Spanner Jan. 14, 1941 2,300,052 Lindebald Oct. 27, 1942 2,541,843 Tiley Feb. 13, 1951 2,557,961 Goldstein et al. June 26, 1951 2,575,383 Field Nov. 20, 1951 2,584,597 Landauer Feb. 5, 1952 2,636,148 Gotham Apr. 21, 1953 2,643,297 Goldstein et al. June 23, 1953 

